Deregulation of the protective immunity of the host is a major concern even after successful anti-retroviral therapy of HIV-1 infected individuals. The proposal is designed to test the hypothesis that induction of antiviral cytokines production would enable the cells to block HIV-1 replication, and may prove to be a significant novel approach to complement anti-retroviral therapy and alleviate AIDS related pathology. As proof of principle we showed (Krasnoselskaya-Riz et al., 2002), that expression of a unique C-terminal variant of NF90, NF90ctv, stimulates interferon response cascade to block HIV-1 replication. We now propose to examine the mechanism of the antiviral response by defining "active" domains of NF90, and the proteins that associate with it to gain a better understanding of the regulation of cellular immune defense. The rationale being, that functional domains of NFg0 that mediate expression of viral resistance genes, do so by association with specific proteins that regulate the endogenous viral inhibitory pathways. The experimental approach will be to utilize: (i) Human CD4+/CXCR4+ cells designed to express FLAG-epitope tagged NF90 to evaluate its effects on HIV-1 replication. (ii) Functional domains of NF90 will be analyzed by studying specific mutants of NF90 and their ability to inhibit HIV-1 replication. (iii) NF90-associated proteins will be affinity fractionated on anti-FLAG antibody columns and analyzed by mass spectrometer. (iv) Biological relevance of NF90-associted proteins will be assessed by competition of NF90-host factor interactions in vivo, utilizing chimeric constructs of the NFg0-domains fused to Drosophila Antennapedia homeodomain peptide, AP-NF90 peptides that are efficiently transported to the nuclear compartment. Proposed studies will identify the cellular pathways that regulate innate antiviral response in human cells and will validate therapeutic approach to augment immune response for HIV-1 resistance.